💏Intro to Chemistry Unit 20 – Organic Chemistry

Key Concepts and Definitions

• Organic chemistry studies compounds containing carbon and their properties, structures, and reactions
• Hydrocarbons consist of only carbon and hydrogen atoms (methane, ethane, propane)
• Functional groups are specific arrangements of atoms within a molecule that give it characteristic properties and reactivity
  • Common functional groups include hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), and carbonyl (C=O)
• Isomers are compounds with the same molecular formula but different arrangements of atoms (structural isomers) or spatial orientations (stereoisomers)
• Nomenclature is the systematic naming of organic compounds based on their structure and functional groups
• Reactions in organic chemistry involve the breaking and forming of chemical bonds, often catalyzed by enzymes or other catalysts
• Organic synthesis is the process of creating complex organic molecules from simpler precursors through a series of chemical reactions

Carbon's Unique Properties

• Carbon has four valence electrons, allowing it to form stable covalent bonds with up to four other atoms
• Carbon can form single, double, or triple bonds with other carbon atoms, enabling the creation of diverse molecular structures
• The ability of carbon to form long chains and rings is the basis for the vast array of organic compounds
• Carbon-carbon bonds are relatively strong and stable, contributing to the stability of organic molecules
• The electronegativity of carbon allows it to form polar covalent bonds with other elements (oxygen, nitrogen, halogens)
• The tetrahedral geometry of carbon atoms in many organic compounds influences their three-dimensional structure and properties
• The presence of carbon in all known life forms on Earth highlights its importance in biological systems

Types of Organic Compounds

• Alkanes are saturated hydrocarbons with only single bonds between carbon atoms (methane, ethane, propane)
  • Alkanes are nonpolar, relatively unreactive, and used as fuels and solvents
• Alkenes contain at least one carbon-carbon double bond and are unsaturated hydrocarbons (ethene, propene)
  • Alkenes are more reactive than alkanes due to the presence of the double bond
• Alkynes have at least one carbon-carbon triple bond and are also unsaturated hydrocarbons (ethyne, propyne)
• Aromatic compounds contain a benzene ring, a six-membered carbon ring with alternating single and double bonds (benzene, toluene, naphthalene)
• Alcohols contain a hydroxyl group (-OH) bonded to a carbon atom (methanol, ethanol, glycerol)
• Carboxylic acids have a carboxyl group (-COOH) and are important in biological systems (acetic acid, citric acid)
• Amines contain an amino group (-NH2) and serve as bases in organic reactions (methylamine, aniline)

Naming Organic Molecules

• The IUPAC (International Union of Pure and Applied Chemistry) nomenclature system is used to systematically name organic compounds
• The longest continuous chain of carbon atoms forms the base name of the compound (meth-, eth-, prop-, but-)
• Functional groups are indicated by specific suffixes (-ol for alcohols, -oic acid for carboxylic acids, -amine for amines)
• Substituents (atoms or groups of atoms that replace hydrogen atoms) are named and numbered based on their position on the main chain
  • Common substituents include alkyl groups (methyl-, ethyl-, propyl-), halogens (fluoro-, chloro-, bromo-), and nitro- groups
• The position of double or triple bonds is indicated by the number of the first carbon atom involved, followed by the suffix -ene or -yne
• Cyclic compounds are named by prefixing the base name with "cyclo-" (cyclopentane, cyclohexene)
• Aromatic compounds are often named based on their common names (benzene, toluene) or by using the prefix "phenyl-"

Chemical Bonding in Organic Compounds

• Covalent bonding is the most common type of bonding in organic compounds, involving the sharing of electrons between atoms
• Sigma (σ) bonds are formed by the direct overlap of atomic orbitals and are the strongest type of covalent bond
  • Single bonds are always sigma bonds
• Pi (π) bonds result from the lateral overlap of p orbitals and are weaker than sigma bonds
  • Double and triple bonds consist of one sigma bond and one or two pi bonds, respectively
• The strength of covalent bonds depends on the electronegativity difference between the bonded atoms and the bond order (single, double, or triple)
• Polar covalent bonds form when there is an unequal sharing of electrons due to differences in electronegativity (C-O, C-N, C-Cl)
• Hydrogen bonding occurs between a hydrogen atom bonded to an electronegative atom (O, N, F) and another electronegative atom, influencing the properties of many organic compounds (alcohols, amines, carboxylic acids)
• Van der Waals forces are weak intermolecular attractions that arise from temporary dipoles and contribute to the properties of organic compounds

Isomerism and Stereochemistry

• Structural isomers have the same molecular formula but different bonding arrangements of atoms (butane and 2-methylpropane)
• Stereoisomers have the same molecular formula and bonding arrangements but differ in the spatial orientation of atoms
  • Geometric isomers (cis and trans) occur when there is restricted rotation around a double bond or ring
  • Optical isomers (enantiomers) are non-superimposable mirror images of each other and have opposite effects on plane-polarized light
• Chirality is the property of a molecule having a non-superimposable mirror image, often due to the presence of an asymmetric carbon atom (a carbon bonded to four different groups)
• The configuration of a chiral center is designated as R (rectus) or S (sinister) based on the priority of the attached groups
• Diastereomers are stereoisomers that are not mirror images of each other and have different physical properties
• The three-dimensional arrangement of atoms in a molecule can significantly impact its biological activity and interactions with other molecules

Common Organic Reactions

• Substitution reactions involve the replacement of one atom or group by another (nucleophilic substitution, electrophilic aromatic substitution)
  • SN1 and SN2 are two common mechanisms for nucleophilic substitution reactions
• Addition reactions occur when atoms or groups are added to a double or triple bond (hydrogenation, halogenation, hydration)
• Elimination reactions involve the removal of atoms or groups from a molecule, often forming a double bond (dehydration, dehydrohalogenation)
• Oxidation reactions increase the oxidation state of a carbon atom by adding oxygen or removing hydrogen (alcohol oxidation, alkene epoxidation)
• Reduction reactions decrease the oxidation state of a carbon atom by adding hydrogen or removing oxygen (alkene hydrogenation, ketone reduction)
• Esterification is the formation of an ester from a carboxylic acid and an alcohol, often catalyzed by an acid
• Hydrolysis is the breaking of a bond by reaction with water, often used to cleave esters or amides

Applications in Everyday Life

• Pharmaceuticals are often complex organic molecules designed to target specific biological receptors or enzymes (aspirin, penicillin, paracetamol)
• Plastics are synthetic organic polymers formed by the polymerization of smaller monomers (polyethylene, polypropylene, polyvinyl chloride)
• Pesticides and herbicides are organic compounds used to control unwanted insects or plants in agriculture (DDT, glyphosate)
• Detergents and soaps are amphiphilic organic molecules that help to remove dirt and grease by emulsifying them in water
• Flavors and fragrances are often volatile organic compounds that interact with olfactory receptors (vanillin, limonene, linalool)
• Dyes and pigments are organic molecules that absorb specific wavelengths of light, producing color (indigo, Prussian blue, Mauveine)
• Fuels such as gasoline, diesel, and natural gas are primarily composed of hydrocarbons and are essential for transportation and energy production
• Organic chemistry plays a crucial role in the development of new materials with desired properties (conductive polymers, liquid crystals, nanomaterials)